This invention relates to a method of making an intraocular lens, and more specifically, a method of making a one-piece intraocular lens.
Intraocular lenses are typically produced by machining and milling the device from a polymer disk that is held in place typically by wax or water (ice) during the fabrication process. Wax, either water soluble wax or solvent soluble wax, is used for fabricating hydrophilic intraocular lenses and ice is used when cryogenically fabricating hydrophobic intraocular lenses, which are rubbers at room temperature and require low temperatures for machining. Each side of the polymer blank is machined and milled in turn, with the final product being a completed single piece intraocular lens.
Typically the milling step, which forms a haptic of the intraocular lens, is performed with an end mill. The mill typically penetrates through the back surface of the machined haptic disk. This partially machined blank is typically held on a second-side mandrel using blocking wax when manufacturing hydrophilic intraocular lenses. Using this method, the wax used and the conditions of milling must be carefully selected in order to minimize adverse effects of the wax on the mill and haptic surface. Also, all swarf and wax must be cleared from the second side surface. Wax is needed to secure the partially fabricated part but also creates problems in the milled haptic, and reduces the tool life of the mill.
After milling, the intraocular lens is deblocked from the wax, which is typically done using solvent or water, depending on the type of wax. Water soluble wax can be problematic because it hydrates the intraocular lens in the presence of the dissolved wax impurities. Using known methods, wax residues must be separately removed from the intraocular lens. The portion of the haptic disk that does not become part of the intraocular lens must also be removed from the finished intraocular lens after deblocking. This is typically a manual process.
Therefore, a need exists for an improved second side mandrel and improvied methods of making intraocular lenses.